U.S. patent number 6,252,689 [Application Number 09/058,468] was granted by the patent office on 2001-06-26 for networked photonic signal distribution system.
This patent grant is currently assigned to Aircuity, Inc.. Invention is credited to Gordon P. Sharp.
United States Patent |
6,252,689 |
Sharp |
June 26, 2001 |
Networked photonic signal distribution system
Abstract
The present invention is a networked photonic signal
distribution system. The system includes a source of light, a light
detector, and an optical distribution network for distributing
light from the source to the detector along a preselected optical
path. The system includes a first plurality of remotely distributed
optical devices that are in optical communication with the optical
distribution network. The optical devices are responsive to at
least one external condition such as a gas, biological agents,
particles, humidity, temperature, air velocity, pressure,
displacement, and proximity or location of objects including people
which can affect a parameter of the available light in the optical
device. The invention further includes a second plurality of
remotely distributed switches for selectably connecting the optical
devices to the optical distribution network. The second plurality
of remotely distributed switches receive the light from the source
of light and convey light that is affected by the external
condition to the optical distribution network and to the detector.
The detector generates output signals in response to the affected
light. The output signals are received by a processor responsive to
signals and generates outputs such as audio or video indications
that are representative of at least one detected external
condition.
Inventors: |
Sharp; Gordon P. (Newton,
MA) |
Assignee: |
Aircuity, Inc. (Newtown,
MA)
|
Family
ID: |
22016990 |
Appl.
No.: |
09/058,468 |
Filed: |
April 10, 1998 |
Current U.S.
Class: |
398/168; 398/107;
398/115; 398/79; 398/9 |
Current CPC
Class: |
G08C
23/06 (20130101); H04B 10/27 (20130101); H04B
10/807 (20130101) |
Current International
Class: |
G08C
23/00 (20060101); G08C 23/06 (20060101); H04B
10/20 (20060101); H04B 10/00 (20060101); H04J
014/02 (); H04B 010/12 () |
Field of
Search: |
;359/126-128,143-145,147,168-170 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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|
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|
0 338 185 |
|
Oct 1989 |
|
EP |
|
0 439 887 |
|
Aug 1991 |
|
EP |
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2 262 676 |
|
Jun 1993 |
|
GB |
|
WO 91/03103 |
|
Mar 1991 |
|
WO |
|
WO 92/18886 |
|
Oct 1992 |
|
WO |
|
WO 93/25020 |
|
Dec 1993 |
|
WO |
|
WO 97/50109 |
|
Dec 1997 |
|
WO |
|
Other References
Uenoya T., "Operation, Administration and Maintenance Systems of
the Optical Fiber Loop", Communications: Connecting The Future,
Dec. 2-5, 1990, vol. 3, Dec. 2, 1990, pp. 1493-1497..
|
Primary Examiner: Pascal; Leslie
Attorney, Agent or Firm: Drinker Biddle & Reath LLP
Claims
What is claimed is:
1. A networked photonic signal distribution system comprising:
a source of light,
a light detector,
an optical distribution network for distributing light from the
source of light to the detector along a preselected optical
path,
a first plurality of remotely distributed optical devices in
optical communication with the optical distribution network for
receiving light therefrom, said optical devices being responsive to
an external condition, said external condition affecting a
parameter of said light, and
a second plurality of remotely distributed switches responsive to
electric signals for selectably connecting said optical devices to
said optical distribution network for receiving light from said
source of light and conveying light affected by said external
condition to said optical distribution network for conveying said
affected light to said detector,
said detector generating output signals in response to said
affected light, and a processor responsive to said detector output
signals for generating outputs representative of said external
condition.
2. The networked photonic signal distribution system as in claim 1
wherein the optical distribution network forms a ring network
structure.
3. The networked photonic signal distribution system as in claim 1
wherein the network forms a bus structure.
4. The networked photonic signal distribution system as in claim 1,
2, or 3 wherein the optical distribution network carries light in a
bi-directional manner.
5. The networked photonic signal distribution system as in claim 1,
2, or 3 wherein the optical distribution network carries light in a
uni-directional manner.
6. The networked photonic signal distribution system as in claim 1
wherein the optical distribution network includes an optical
fiber.
7. The networked photonic signal distribution system as in claim 1
wherein said external condition is selected from the group
consisting of containment of a laboratory hood, gas, particulate,
quality of air in a building.
8. The networked photonic signal distribution system as in claim 1
wherein said source of light comprises a single source located at
an input to the optical distribution network for generating all of
the light conveyed by the optical distribution network.
9. The networked photonic signal distribution system as in claim 1
wherein said remotely distributed switches are electro-optical
switches.
10. The networked photonic signal distribution system as in claim 1
wherein said light detector comprises a single detection device at
an output of said optical distribution network.
11. The networked photonic signal distribution system as in claim 1
wherein said plurality of remotely distributed optical devices are
integrated with an airflow control device for sensing airflow
passing through the airflow control device.
12. The networked photonic signal distribution system as in claim 1
wherein said first and second plurality are equal in number.
13. The networked photonic signal distribution system as in claim 1
wherein the source of light generates a plurality of
wavelengths.
14. The networked photonic signal distribution system as in claim 1
wherein the said plurality of remotely distributed optical devices
comprises a number of different devices for responding to different
external conditions.
15. The networked photonic signal distribution system as in claim 1
wherein at least one of the plurality of optical devices responds
to a plurality of external conditions.
16. The networked photonic signal distribution system as in claim 1
wherein the optical distribution network has a plurality of optical
paths coupled into a routing device.
17. The networked photonic signal distribution system as in claim
16 wherein the routing device comprises a coupler.
18. The networked photonic signal distribution system as in claim
17 wherein the routing device comprises a switch.
19. The networked photonic signal distribution system as in claim 1
wherein the optical distribution network forms a tree network
structure.
20. The networked photonic signal distribution system as in claim 1
wherein the optical fiber further comprises at least one optical
amplifier.
21. The networked photonic signal distribution system as in claim
20 wherein said optical amplifier is an erbium-doped optical-fiber
amplifier.
22. The networked photonic signal distribution system as in claim
20 wherein said at least one optical amplifier has two
unidirectional optical amplifiers.
23. The networked photonic signal distribution system as in claim 1
further comprising,
a third plurality of remotely distributed data communication and
control devices in communication with said switches for controlling
the operation thereof in response to preselected data signals,
and
a command unit for coordinating the operation of the data
communication and control devices in a preselected manner.
24. The networked photonic signal distribution system as in claim
23 where in the third plurality is equal in number to said second
plurality.
25. The networked photonic signal distribution system as in claim
23 wherein the preselected data signals are in electrical form.
26. The networked photonic signal distribution system as in claim
23 wherein the command unit comprises a preselected one of said
third plurality of data communication and control devices.
27. The networked photonic signal distribution system as in claim
23 wherein the data and communication control devices comprise
non-dedicated modules, said modules performing functions in
addition to operating said optical switches.
28. The networked photonic signal distribution system as in claim
27 wherein the data and communication control devices control the
ventilation system in a building.
29. The networked photonic signal distribution system as in claim
23 wherein the command unit comprises a programmable device.
30. The networked photonic signal distribution system as in claim
29 wherein the programmable device comprises a computer.
31. The networked photonic signal distribution system as in claim
23 wherein the preselected data signals are in optical form.
32. The networked photonic signal distribution system as in claim
31 wherein the preselected data signals in optical form are
conveyed along said optical distribution network.
33. The networked photonic signal distribution system as in claim
32 wherein the preselected data signals in optical form are at a
wavelength different from the wavelengths of the light distributed
by the optical distribution network.
34. The networked photonic signal distribution system as in claim
as in claim 32 wherein the light distributed by the optical
distribution network is used to create said preselected data
signals in optical form.
35. The networked photonic signal distribution system as in claim
23 wherein said data communication and control devices receive
radio frequency signals for wireless operation.
36. The networked photonic signal distribution system as in claim 1
wherein said plurality of remotely distributed optical devices
generate a light beam across a portion of an area to be sensed.
37. The networked photonic signal distribution system as in claim
36 wherein the area to be sensed is in an air duct.
38. The networked photonic signal distribution system as in claim 1
wherein said plurality of remotely distributed optical devices
include an averaging chamber where air is sampled as it is drawn
through the averaging chamber.
39. The networked photonic signal distribution system as in claim
38 wherein a pressure drop across an airflow control device is used
to draw air through the averaging chamber.
40. The networked photonic signal distribution system as in claim 1
wherein said plurality of remotely distributed optical devices
include a section of optical fiber responsive to an external
condition.
41. The networked photonic signal distribution system as in claim 1
wherein a portion of said plurality of remotely distributed
switches are replaced by optical couplers.
42. The networked photonic signal distribution system as in claim 1
wherein said source of light is a laser diode having a variable
wavelength.
43. The networked photonic signal distribution system as in claim 1
wherein said source of light is a vertical cavity surface emitting
diode.
44. The networked photonic signal distribution system as in claim 1
wherein said output signal is used to improve the environment in a
building.
45. The networked photonic signal distribution system as in claim 1
wherein said output signal is used to control an industrial or
manufacturing process.
46. The networked photonic signal distribution system as in claim 1
wherein said output signal is used to indicate the environment in a
plurality of residential housing units.
47. The networked photonic signal distribution system as in claim 1
wherein said plurality of remotely distributed optical devices have
a reflective element for use in a bidirectional network.
48. The networked photonic signal distribution system as in claim 1
wherein multiple areas are simultaneously monitored.
49. The networked photonic signal distribution system as in claim
48 wherein at least two of said switches are energized
simultaneously.
50. The networked photonic signal distribution system as in claim 1
wherein the network comprises combinations of bus and tree
structures.
51. The networked photonic signal distribution system as in claim 1
wherein said source of light include pulsed light signals.
52. A networked photonic signal distribution system for measuring
at least one external condition in at least one space, the system
comprising:
a source of light,
a light detector,
an optical distribution network for distributing light from the
source of light to the detector along a preselected optical path,
said optical path extending into at least one space,
a first plurality of remotely distributed optical devices in
optical communication with the optical distribution network for
receiving light therefrom, said optical devices being responsive to
at least one external condition, said at least one external
condition affecting a parameter of said light, and
a second plurality of remotely distributed switches responsive to
electrical signals for selectable connecting said optical devices
to said optical distribution network for receiving light from said
source of light and conveying light affected by said at least one
external condition to said optical distribution network for
conveying said affected light to said detector,
said detector generating output signals in response to said
affected light, and a processor responsive to said detector output
signals for generating outputs representative of said at least one
external condition.
53. The networked photonic signal distribution system as in claim
52 wherein said at least one space is at least one building.
54. The networked photonic signal distribution system as in claim
52 wherein said at least one space is at least one preselected area
in at least one building.
55. A networked photonic signal distribution system comprising:
a light source means,
a light detector means,
an optical distribution network means for distributing light from
the light source means to the detector means along a preselected
optical path,
a first plurality of remotely distributed optical device means in
optical communication with the optical distribution network means
for receiving light therefrom, said optical device means being
responsive to an external condition, said external condition
affecting a parameter of said light, and
a second plurality of remotely distributed switch means responsive
to electrical signals for selectably connecting said optical device
means to said optical distribution network means for receiving
light from said light source means and conveying light affected by
said external condition to said optical distribution network means
for conveying said affected light to said detector means,
said detector means generating output signals in response to said
affected light, and a processor means responsive to said detector
output signals for generating outputs representative of said
external condition.
56. A method of distributing a photonic signal in a networked
distribution system comprising the steps of:
generating light,
distributing the light through an optical distribution network
along a preselected optical path,
receiving the light by a first plurality of remotely distributed
optical devices in optical communication with the optical
distribution network, the optical devices being responsive to an
external condition,
affecting a parameter of the received light when the optical device
is responsive to the external condition,
connecting, in a selectable manner, a second plurality of remotely
distributed electrically actuated switches that connect the optical
devices to the optical distribution network,
conveying the light affected by the external condition on the
optical distribution network to a light detector,
detecting the affected light and generating output signals in
response to said affected light, and
processing the output signal with a processor to generate outputs
representative of the external condition.
57. A networked photonic signal distribution system comprising:
a source of light,
a light detector,
an optical distribution network for distributing light from the
source of light to the detector along a preselected optical
path,
a first plurality of remotely distributed optical devices in
optical communication with the optical distribution network for
receiving light therefrom, said optical devices being responsive to
an external condition, said external condition affecting a
parameter of said light, and
a second plurality of remotely distributed electro-optical switches
for connecting said optical devices to said optical distribution
network for receiving light from said source of light and conveying
light affected by said external condition to said optical
distribution network for conveying said affected light to said
detector,
said detector generating output signals in response to said
affected light, and a processor responsive to said detector output
signals for generating outputs representative of said external
condition.
58. The networked photonic signal distribution system as in claim
57 wherein said remotely distributed electro-optical switches are
controlled by electrical signals derived from the light distributed
by the optical distribution network.
59. A networked photonic signal distribution system comprising:
a source of light,
a light detector,
an optical distribution network for distributing light from the
source of light to the detector along a preselected optical
path,
a first plurality of remotely distributed optical devices in
optical communication with the optical distribution network for
receiving light therefrom, said optical devices being responsive to
an external condition, said external condition affecting a
parameter of said light,
a second plurality of remotely distributed switches for selectably
connecting said optical devices to said optical distribution
network for receiving light from said source of light and conveying
light affected by said external condition to said optical
distribution network for conveying said affected light to said
detector,
a third plurality of remotely distributed data communication and
control devices in communication with said switches for controlling
the operation thereof in response to preselected electrical data
signals, and
a command unit for coordinating the operation of the data
communication and control devices in a preselected manner,
said detector generating output signals in response to said
affected light, and a processor responsive to said detector output
signals for generating outputs representative of said external
condition.
60. A networked photonic signal distribution system comprising:
a source of light,
a light detector,
an optical distribution network for distributing light from the
source of light to the detector along a preselected optical
path,
a first plurality of remotely distributed optical devices in
optical communication with the optical distribution network for
receiving light therefrom, said optical devices being responsive to
an external condition, said external condition affecting a
parameter of said light,
a second plurality of remotely distributed switches for selectable
connecting said optical devices to said optical distribution
network for receiving light from said source of light and conveying
light affected by said external condition to said optical
distribution network for conveying said affected light to said
detector,
a third plurality of remotely distributed data communication and
control devices in communication with said switches for controlling
the operation thereof in response to preselected electrical data
signals,
an electrical network in communication with said third plurality of
remotely distributed data communication and control devices for
communicating said preselected data signals, and
a command unit for coordinating the operation of the data
communication and control devices in a preselected manner,
said detector generating output signals in response to said
affected light, and a processor responsive to said detector output
signals for generating outputs representative of said external
condition.
Description
FIELD OF THE INVENTION
The present invention relates generally to a signal distribution
system, and more particularly to a networked photonic signal
distribution system for sensing an ambient condition affecting a
parameter of light.
BACKGROUND OF THE INVENTION
It is of great importance to our health and safety to know the
condition and habitability of our environment. In particular, much
effort and expense has been expended in the past to control and
detect pollutants in air. For example, in residential housing units
including homes, office buildings, or buildings that have
laboratories or where dangerous chemicals are stored, the need to
monitor the air for smoke or contamination is very great. It is
also necessary that air sensing be accurate and rapid which is a
particular challenge in multiple spaces such as individual rooms in
large office or apartment buildings.
Early attempts to address this need have produced systems capable
of detecting poor ventilation in buildings by simple means, usually
indicating excess CO.sub.2 levels or VOC's (Volatile Organic
Compounds), excess particulates, or other dangerous gaseous
materials. However, these early continuous monitoring systems were
often expensive, difficult to install, and not known to be accurate
or reliable due to the nature of the individual sensors themselves
or the calibration required of these sensors.
Systems for sensing air quality are shown in U.S. Pat. Nos.
3,683,352; 3,781,092; 3,805,066; 4,027,153; 4,403,806; 4,516,858;
4,641,025; and 4,820,916, United Kingdom patent application GB
2,215,038, and German Patent DE 3409-618-A1.
U.S. Pat. No. 3,683,352 discloses an alarm system for sensing smoke
and intruders. The '352 patent teaches the use of a single light
beam source for transmitting light through remote light-to-electric
transducers for detecting smoke and intruders passing through the
light beams between the transducers. Detection of an intruder or
smoke is indicated by an amplitude or polarization modulation of
the light signal at a characteristic frequency.
U.S. Pat. No. 3,781,092 discloses a monitoring system having a
plurality of independent optical fiber paths, transducers, optical
shutters, and modulators in combination with a common laser light
source. Light is emitted by the common source and split among the
various fiber light paths present in the system. The light travels
through the fiber light path to the transducer which encodes
information onto the light by means of an optical switch.
U.S. Pat. No. 3,805,066 discloses a smoke detecting device using a
plurality of optical fibers arranged in a series alignment leaving
gaps therebetween. A light signal is transmitted through the fiber
for detection of smoke by a photo-electric transducer located at
the terminal end of the series alignment.
U.S. Pat. No. 4,027,153 discloses a fiber network having a passive
optical coupler for the transmission of data between addressable
subscriber stations present in the system. Each station has a
transmitter and receiver and a specific address code for
identification. Information from the stations is sampled cyclically
by a common addressing unit also connected to the stations via the
passive optical coupler.
U.S. Pat. No. 4,403,806, discloses a visibility measurement
apparatus having a central unit for controlling an emitted light
signal and a plurality of transmitter and receiver units for
measuring the attenuation of the emitted light signal. The
centralized unit emits the light signal which is transmitted and
received by the transmitter and receiver units and returned to the
central unit for evaluation.
U.S. Pat. No. 4,516,858 discloses a multiple site laser-excited
pollution monitoring system having a central laser source and a
plurality of optical fibers. The laser emits a light signal that is
deflected in timed sequence to a plurality of remote laser-excited
photo-acoustic detector heads for detecting vapor by Raman
scattering, fluorescence, absorption, and photoionization. The
detector heads transmit a detection signal by electric wires to a
signal processor and display unit that are also located at a
central location.
U.S. Pat. No. 4,641,025 discloses a system for determining the
position of the boundary between substances having different
refractive indices. The '025 patent discloses a plurality of
optical sensors, a common pulse source, and an interface responsive
to the source pulse and for producing a response pulse that is
delivered to common receiver. The receiver measures the duration of
the response pulse having a time duration that is proportional to
the number of sensors in the system. The position of the boundary
is determined by calculating the time duration in response to a
fixed and known number of sensors.
U.S. Pat. No. 4,820,916 discloses an optically powered sensor
system having a plurality of sensors connected to an optical bus
for communication with a system controller. Optical energy is
transmitted on the bus and distributed to the sensors system-wide.
The sensors have a photodiode array for sensing a measurable
parameter and providing an optical pulse signal as a function of
the measured parameter. The sensors include a transducer and a
pulse encoder for producing a series of short duration pulses to
drive an optical source for transmitting corresponding optical
pulses to the system controller. The patent provides for a
multi-sensor configuration by providing sensor-specific time delay
prior to the transmission of the return pulse from the sensor to
the controller. The time delay provides a predetermined time window
for each sensor allowing sensor discrimination.
United Kingdom patent application GB 2,215,038 discloses an optical
sensing system including a central light source emitting broadband
light over a plurality of light paths that are terminated in a
common Fabry-Perot cavity filter having scanning and detector means
for scanning a narrow bandwidth of the broadband light.
German Patent DE 3409-618-A1 discloses a fiber optic measurement
system having a plurality of optical fibers connected to a
plurality of optical sensors and light sources having different
emission spectra selected according to the desired absorption and
transmission characteristics of the sensors.
In addition to installed systems, other approaches for sensing the
air quality in the past have included hand-held sensing
instruments. However, these are expensive and awkward devices to
use, particularly when long term multi-room monitoring is desired.
Another approach used in the past is individual OEM type sensor
instruments connected into some type of data gathering and or
control system. However, these systems are also very costly if many
rooms must be monitored simultaneously, since costly sensors are
required in each room that is monitored. In addition, cost and
complexity dramatically increase when more than one gas is to be
sensed and monitored. Furthermore, operating costs of these systems
are also high due to the large amount of field work required to
continually recalibrate the large volume of sensors that are
employed.
Recently, many types of new sensors have been developed or proposed
that use optical techniques with light from lasers or other light
sources. In many cases the light emitted from these sources can be
transported and guided by the use of fiber optic cable made of
plastic, glass or other compounds. This allows the emitter and/or
detector to be remotely located from the area to be sensed. It also
potentially allows the use of techniques to multiplex the use of
one set of gas or particle light emitters and detectors over many
measurement sites or locations. Current multiplexing approaches
have included, for example, Wavelength Division Multiplexing where
many distinct light signals each of a different wavelength are
created and sent in to a fiber system with multiple sensors. Each
sensor can respond to a different wavelength signal. These modified
signals are then demultiplexed at the common detector location and
individually sensed.
In another example, Time Division Multiplexing (TDM) is used to
send a very short light pulse into a multiple fiber (1XN) beam
splitter or coupler which creates multiple copies of the pulse on
multiple fibers connected to the coupler. After passing through a
sensor located on each one of these multiple fibers, all the
modified pulses are recombined by another multiple fiber (1XN)
coupler back onto one return fiber. As long as the path lengths of
the multiple fiber-sensor paths are different, the result will be a
pulse train of individually modified pulses on the single return
fiber. By using time and path length the affected pulses can be
matched to the appropriate sensor to detect and determine a
particular condition or substance at the sensor's location.
These two multiplexing approaches are complex, expensive, and are
not general purpose due to the wavelength or time limitations of
the technique. Consequently they are not readily adapted to
changing environmental sensing requirements in a building.
To avoid these types of limitations and complexity other systems
have been developed that use optical switches to switch one of many
fibers coming from a remote location to a common emitter or
detector. These approaches use an optical switch which can switch a
light beam from one fiber to another one of several other fibers
with minimal loss and affect on the transmitted light. These
approaches specifically locate the multiplexing switch near the
emitter and or detector and use a multitude of fiber cables leading
from the central location to the sensed locations. This approach
although simpler and more flexible than the previous approaches
suffers from the need to locate a vast amount of fiber cables
throughout the building. If a new location is to be added it
requires the installation of another fiber cable between the
central location and the new sensed location.
The present invention addresses and solves many of the
above-mentioned problems associated with prior art systems.
SUMMARY OF THE INVENTION
The present invention is a networked photonic signal distribution
system. The system employs commercially available and economical
optical switches, optical fiber, and a common emitter and detector.
Remotely distributed optical switches are used to switch a light
beam from one fiber to another with minimal loss at a sensed
location to effect a difference in the light beam which is used to
determine a particular condition or substance. This system is
particularly useful for detecting a plurality of pre-selected
conditions or substances in an area such as the ambient space about
a test chamber in a laboratory, the rooms in a building, an entire
building or several buildings instantaneously. It is understood
that the invention can be used for homes, including multiple
residential dwelling units, office buildings and the like. The
invention can also be used to control an industrial or
manufacturing process.
This system can greatly reduce the complexity and cost of
environmental control and detection systems. First of all it can
dramatically reduce the amount of fiber cable required as well as
creating a much more flexible system that can be added to easily
without running long lengths of cable. Furthermore, the control of
the sensing network is totally flexible and programmable. Unlike
the above multiplexing approaches that in effect try to sense all
sensor locations virtually simultaneously, this new approach is a
selective approach where locations are sensed either sequentially
in a programmed pattern or are selected in real time. This system
is consequently more flexible in its applications. If desired many
of the before mentioned time division and wavelength division or
frequency multiplexing schemes can still be used with this
approach.
Another advantage of this approach is that the optical loss of the
switches is much less than the loss of the couplers used in the
multiplexer concepts previously described. In TDM or WDM approaches
the source light must pass through all the sensors simultaneously,
consequently couplers are used to split the beam into each sensor.
The power division of this system means that very little light
reaches each sensor drastically limiting the number of potential
sensing locations that are usable. In the new approach, by contrast
the optical switches route all the optical power of the source to
the sensed location. The only loss of power is due to the insertion
losses of the switches which are in comparison quite small compared
to the power division losses of the couplers.
Lastly, the new approach is quite economic by potentially using the
control capabilities of a building, critical spaces or laboratory
airflow control system's control and data communications network to
control the fiber network's optical switches and hubs. This means
that this control function comes almost for free since these
building control networks will need to be installed in these
buildings whether the photonic environmental sensing network is
desired or not. The cost of the additional control outputs needed
for the photonic network will be a very minor amount of additional
cost to these systems.
Rather than use the previously mentioned "single star" method where
all fiber emanates from a single location with all switching
centralized at the emitter/detector location, the new approach can
use a bus, ring or cascaded star using multiple secondary or
tertiary hubs to create a lower cost and more flexible approach.
All of these new approaches share the characteristic that at least
some of the optical switching is done remotely from the central
emitter and/or detectors. These remote switches may be self
controlled due to some pre-configured algorithm or more likely they
can be controlled by a control and data communications network. In
the preferred embodiment this control and communication is done
through a separate overlaid electronic or perhaps optical control
and data communications network with control/data communication
nodes located near the optical switches. Alternatively this control
and data communication can also be achieved through the photonic
signal distribution network using techniques such as wavelength
division multiplexing to run the controls signals at a different
wavelength from the gas or particle sensing wavelengths.
The networked photonic signal distribution system previously
mentioned has a source of light, a light detector, and an optical
distribution network for distributing light from the source to the
detector along a preselected optical path. The system includes a
first plurality of remotely distributed optical devices that are in
optical communication with the optical distribution network. The
first plurality of remotely distributed optical devices receive
light from the optical distribution network. The optical devices
are responsive to an external condition such as but not limited to
gas or particles which affect a parameter of the available light in
the optical device.
The invention includes a second plurality of remotely distributed
switches for selectably connecting the optical devices to the
optical distribution network. The second plurality of remotely
distributed switches receive the light from the source of light and
convey light that is affected by the external condition to the
optical distribution network and to the detector. The detector
generates output signals in response to the affected light. The
output signals are received by a processor responsive to signals
and which generates outputs such as audio or video indications that
are representative of the external condition.
The invention also includes, when required, a separate control
network comprised of a fiber or electrical network such as a
coaxial cable or a multi-conductor twisted line, in parallel with
the photonic signal distribution system network for an alternate
means of control of the remotely distributed switches. This control
network would typically operate on a data communications basis with
appropriate network protocols to pass data to and between the
control/data communications devices. This network could be
dedicated to the control of the photonic signal distribution system
network or could be also used for other functions as well such as
environmental controls in the building or for data networking
between office Personal Computers or Workstation.
In an alternate embodiment, control of the remotely distributed
switches can be accomplished through special encoding of the light
signals that are being passed along the photonic signal
distribution system network itself. This approach has the advantage
of eliminating another separate fiber or electrical twisted pair
control path.
In another alternate embodiment, either the common emitter or
detector is replaced with either individual emitters or detectors
at the sensed locations to eliminate the need for either a
supplying or a returning path of photonic signal from the
distribution network. Where individual emitters are used at the
sensed locations an on/off control for the emitters may (depending
on the network architecture) be used to replace all or a portion of
the network optical switches.
BRIEF DESCRIPTION OF THE DRAWINGS
For the purpose of illustrating the invention, there is shown in
the drawings a form which is presently preferred; it being
understood, however, that this invention is not limited to the
precise arrangements and instrumentalities shown.
FIG. 1 illustrates a networked photonic signal distribution system
according to the present invention having a series network
structure.
FIG. 2 illustrates a networked photonic signal distribution system
according to an alternate embodiment of the present invention
having a cascaded star network configuration.
FIG. 3a illustrates a networked photonic signal distribution system
according to an alternate embodiment of the present invention
having a hybrid network of series and cascaded star network
structures.
FIG. 3b illustrates a networked photonic signal distribution system
according to an alternate embodiment of the present invention
having networked data communication and command units.
FIG. 4 illustrates a 1-X-n optical hub switch.
FIG. 5 illustrates an optical switch connecting a unidirectional
optical fiber to an optical gas sensing cell and an optical
bypass.
FIG. 6 illustrates an optical switch connecting a bidirectional
optical fiber to a bidirectional optical circulator having a
transmissive gas sensing cell.
FIG. 7 illustrates an optical device having a one port reflective
gas sensing cell.
FIG. 8 illustrates an optical switch connecting a bidirectional
optical fiber to another bidirectional optical fiber and a one port
reflective gas sensing cell.
FIG. 9 illustrates a bidirectional optical circulator/coupler
connecting a source of light, a detector system, and a command
unit.
FIG. 10 illustrates a six port optical switch connecting an optical
device and two optical fibers operating in a duplex optical
network.
FIG. 11 illustrates a star coupler and a blocking switch having a
first position bidirectional path and a second position path
termination.
FIG. 12 illustrates an optically controlled switch system having a
coupler, a switch controller, and an optical switch providing a
through path to another switch and an optical device.
FIG. 13 illustrates common source, detection, and command units
having multiple detectors, sources, and a network command unit
which communicate over the same fiber path and have a wavelength
division multiplex configuration.
FIG. 14 illustrates a bidirectional optical amplifier system with
two unidirectional optical amplifiers.
FIGS. 15a-15c illustrate optical paths formed in an air flow
control device having a gas sensing cell.
FIG. 16 illustrates an optical path formed in an air valve having a
gas sensing cell.
DETAILED DESCRIPTION OF THE INVENTION
The present invention is a networked photonic signal distribution
system for detecting a plurality of pre-selected conditions or
substances in an area such as contaminant control of a fume hood,
the ambient space about a test chamber in a laboratory, the rooms
in a building, an entire building or several buildings. Referring
now to the drawings, wherein like numerals indicate like elements,
there is shown in FIG. 1 an illustration of a networked photonic
signal distribution system 10 having a photonic signal distribution
network 20 and a common light source, detection, and command unit
30.
The photonic signal distribution network 20 includes an optical
fiber 22, and a plurality of optical switches 50 and optical
devices 60. The common source, detection, and command system 30
includes a light source system 100, a detection system 200, and a
network communication and command unit 300. In a preferred
embodiment of the networked photonic signal distribution network
system 10, the light source 100 is connected to the optical fiber
22 and emits light 110 that is distributed by the distribution
network 20 to the plurality of optical switches 50 and optical
devices 60. The light 110 is affected 110' by a condition in
optical contact with the optical device 60. The affected light 110'
is carried by the distribution network 20 where it is detected by
the detection system 200. The affected light is then used, or
communicated to some other device, by the system 10 to indicate or
otherwise communicate a detected condition.
In one aspect of the invention, a first plurality of remotely
distributed optical devices 60 are in optical communication with
the optical distribution network 20. The optical devices 60 receive
the light 110 from the optical distribution network 20 by means of
an optical switch 50. Specifically, each individual optical device
60a, 60b, . . . 60n is independently responsive to a proximate
external condition 400a, 400b, . . . 400n which affects a parameter
of the light 110 to produce individually affected light 110'. The
external condition 400a, 400b, . . . 400n may include, but is not
limited to CO.sub.2 levels or VOC's (Volatile Organic Compounds)
other gaseous materials, bacterial agents, temperature, humidity,
air velocity, air pressure or particulates.
A second plurality of remotely distributed switches 50 selectably
connect the optical devices 60 to the optical distribution network
20. Each remotely distributed switch 50a, 50b, . . . 50n receives
the light 110 from the source of light 100. The remotely
distributed switches 50a, 50b, . . . 50n also convey the affected
light 110' that is affected by the external condition 400a, 400b, .
. . 400n to the optical distribution network 20. The optical
distribution network 20 conveys the affected light 110' to a light
detector in the detection system 200.
In response to the affected light 110', the detection system 200
generates output signals by means of a processor unit 290 shown in
FIG. 9 and described in more detail below. This processor 290
generates outputs representative of the external condition 400a,
400b, . . . 400n. These outputs may be in analog signal or digital
information format. The digital information may be conveyed to a
building or facility management system for use or display to an
operator or directly to a computer such as a Personal Computer or
workstation for further analysis and/or display to an operator.
In another aspect of the preferred embodiment, each remotely
distributed switch 50a, 50b, . . . 50n is connected to and
controlled by a data communications and command unit 310a, 310b,
310n. These units may be dedicated solely for this system or may
have another use such as in helping to control aspects of the
building or be part of Personal Computers or Workstation which are
networked together. As shown in FIG. 1 the data units 310a, 310b, .
. . 310n will typically be connected to the command unit 300 by
means of a separate data communications network 24. The data
communications network 24 can be an electrical or a fiber network,
and convey electrical or optical preselected data signals that are
generated by the command unit 300 to control the remotely
distributed switch 50a, 50b, . . . 50n.
Network Structures
In one aspect of the networked photonic signal distribution system
10, the optical distribution network 20 forms a bus or a ring
network structure as shown in FIG. 1. The ring network structure
includes a plurality of electro-optical switches 50 and devices 60
connected in series along the optical fiber 22.
If a room is to be sensed, the optical switch 50 may route the
light into the room into an optical device 60 connected to a gas
sensing cell such as that shown in FIG. 7. It is understood that
other gas sensing devices can be used such as, but not limited to,
a segment of special optical fiber that is affected by its
immediate environment; or an apparatus that sends the light beam
across a duct, an airflow controller device, a valve in the duct,
or through a portion of the room itself. The light is then sent
back into the switch 50 and then to the next optical switch 50 in a
unidirectional approach or reflected back to the source in a
bi-directional implementation. FIG. 5 shows a diagram of a
unidirectional optical switch used for unidirectional networks and
FIGS. 6 and 8 show a bidirectional optical switch used for
bidirectional networks.
If a particular room is not to be sensed, the optical switch 50
allows the light beam to bypass the room and go on to the next
room. One of the factors for consideration in this structure is the
optical attenuation loss that occurs as the light signal passes
through the network. The most important part of this loss is the
bypass insertion loss of the optical switches 50. Typical insertion
loss for these units, including connector loss, can vary from 0.5
dB to a more typical value of about 1.0 dB to more than 2.5 dB
depending on the type of optical switch technology employed. The
complexity of the optical switch also affects the amount of loss.
For example, a unidirectional optical switch like that shown in
FIG. 5 will have twice the internal loss of a bidirectional optical
switch like the ones shown in FIG. 6 or 8. This is caused by the
typical use of a second switch in unidirectional optical switch
devices. In the unidirectional switch approach, the detector should
be at the end of the system. If the detector is located in the same
unit as the light emitter then the bus will form a ring shape.
Referring to FIG. 1, the optical fiber 22 forms a bus structure
making a full loop or ring that typically starts and ends at the
location of the light source system 100 and detection system 200.
The advantage of a ring configuration over a bi-directional system
is that the path length is shorter by twice on average for the
entire network. In addition, the path has a fixed length no matter
which room is being sensed.
Referring to FIG. 2, the networked photonic signal distribution
system 10 can have an optical distribution network 20 that is
formed into a cascaded star network structure. The star network
structure includes a plurality of electro-optical switches 500,
510, 520 (referred to as hub switches), that are connected to the
optical fiber 22 to form parallel branches or tree-like network
structures using the optical fiber 22. Unlike a single massive star
approach with many fibers emanating from a single location, the
tree structure uses much less cable due to the use of floor hubs
510, and sub-floor hubs 520 when needed. These lower level hubs or
"branches" can be optimally placed to minimize cable runs in the
network in many applications such as in buildings. The
electro-optical hub switches 500, 510, 520 act as routing devices
which can create a plurality of optical paths that form the optical
distribution network 20. Typically, the electro-optical hub
switches 500, 510, 520 are 1-X-N optical switch devices as shown in
FIG. 4
Referring to FIG. 2, a building switch 500 routes the light beam
from the common source, detection, and command system 30 to one of
several floors, or sections of a floor, via an optical fiber 22
emanating from one of the output ports of the building switch 500.
A secondary hub 510 on the two lower floors, switches the beam to
one of a set of subfloors or tertiary hubs 520 that switch the beam
into the actual room that is to be sensed. In this approach all the
optical switching is done by the hubs 510, 520.
The electro-optical hub switches 500, 510, 520 can be identical in
type, such as a 1-X-N switching device and are distinguished from
one another by their location and function in the network. The
outputs of electro-optical hub switches 500, 510, 520 are connected
by means of the optical fiber 22 to a plurality of optical devices
60a, 60b, 60n that are independently responsive to a proximate
external condition 400a, 400b, . . . 400n that effect a parameter
of the light 110 thereby producing affected light 110'. The star
switches 500, 510, 520 are controlled by a data communications and
command unit 310 as shown in FIG. 2. The data communications and
command units 310 are connected to the command unit 300 by means of
separate electrical or fiber control networks 24.
Referring to FIGS. 3a and 3b, electro-optical hub switches 500,
510, and 520 can be arranged in a multi-level building having an
optical distribution network 20 with both a bus and tree network
structure. In such an arrangement, a networked photonic signal
distribution system 10 can be used in a multi-level building having
a common source, detection, and command system 30 that is connected
by an optical fiber 22 to a 1-X-N base electro-optical hub switch
500.
In FIG. 3a, the first and second floor of the building has floor
switches 510 that are connected to a tier of star switches 520 that
are connected, by means of an optical fiber 22, to subfloor
switches which are connected to a bus network of optical switches
50a, 50b, . . . 50n. The third floor of the building has outputs of
the electro-optical hub switches 500 that are connected to a
plurality of remotely distributed floor hub switches 510. The hub
switches 510 can then in turn be connected directly to a smaller
bus type network having single optical switches 50a, 50b, . . . 50n
that are also connected to a plurality of optical devices 60a, 60b,
. . . 60n.
Optical switches, including hub switches 500, 510, 520 or
individual optical switches 50a, 50b, . . . 50n, are controlled
through a network of control and data communications units 310 as
shown in FIG. 3b. Each of the control and data communications units
310 can be connected to at least one optical switch 500, 510, 520
as shown in FIG. 3b, or an optical switch 50 as shown in FIG. 3a.
The connection between the control and data communications unit 310
and an optical switch can be through line 150 as shown in FIGS. 8
and 11. It is to be understood that one data communication and
command unit 310 may contain multiple outputs 150 which are used to
control multiple optical switches of either hub and/or single
optical switch units like those shown in FIGS. 1-3. As shown in
FIG. 3b, a router function may also be implemented by means of a
router unit 311 that segments the electrical or fiber networks 24
to create three individual networks.
As mentioned earlier, a hybrid network may be formed by combining a
cascaded star and series network structures as shown in FIG. 3a and
3b. In practice this approach, or variations of this approach, may
provide the most flexibility for optical network applications. For
example, in one application a cascaded star structure is used to
bring emitted light 110 into a particular room. Within the room a
bus structure might be used to pick up multiple sample points
within the room. Alternatively, it may be more economical to
reverse this structure and use a small bus along a portion of a
floor coming off from a floor based hub. Within a room a small star
structure is then used to pick up multiple points within the room
itself. This may be more economical based on wiring costs since the
points off from the intra-room star do not have far to go. Either
or both options may be selected depending on the individual
specifics of a room and floor situation to optimize the costs of
wiring, optical cable, and component insertion losses.
Often, but not necessarily, the number of remotely distributed
switches 50 equals the number of optical devices 60. Having an
equal number of remotely distributed switches 50 and optical
devices 60 is not essential. The optical distribution network 20
can have a combination of electro-optical hub switches 500, 510,
520 that can be directly connected to an optical device 60 or to a
remotely distributed switch 50 that is itself connected to a
plurality of optical devices 60a, 60b, . . . 60n connected in
series or parallel for example. Depending on the configuration of
the optical distribution network 20 selected, the light 110'
effected by the external condition 400a, 400b, . . . 400n can be
coupled to the optical distribution network 20 through the remotely
distributed switches 50 or hub switches 500, 510, 520, or directly
from the optical devices 60.
FIGS. 2 and 3 show bidirectional networks with light traveling in
both directions in the same fiber simultaneously. In these networks
the optical devices 60 may have air or gas sensing cells, an open
path cell, or a fiber sensor that would have a reflective mirror or
some means allowing the light 110 to be affected by some condition
and sending the affected light 110' back through the network for
detection. The emitted light 110 can be separated from the affected
light 110' by means of a beam splitting circuit like that shown
FIG. 9 described in detail below. An approach for a reflective gas
sensing cell is shown in FIG. 7 (described later). Other reflective
approaches can be used such as single termination devices which are
inherently designed to reflect light back through their
input/output port.
One advantage provided by the cascaded star approach shown in FIGS.
2 and 3 over the bus or ring structure of FIG. 1 is that a large
amount of nodes can be accommodated with minimal loss caused by
optical switches. This is partially due to the use of optical 1XN
hub or star switches that have the same insertion loss of a simple
SPDT or 1X2 optical switch used in the bus or ring switches.
By way of example, a 100 node ring network would encounter a loss
of 100 dB due to a 1 dB insertion loss from each optical switch. On
the other hand, the structure shown in FIG. 2 with three levels of
hubs, each having 5 outputs (1.times.5 switches), could accommodate
125 nodes. If the insertion loss of each hub is 1 dB the insertion
loss of the system due to the switches would only be 6 dB if each
hub had a 1 dB loss. This results from 3 dB of loss to get to the
end node and 3 dB more loss to get back to the detector. Although
more cable would be used in this system, the overall attenuation
loss is less. Additionally, since the actual signal path length is
shorter, the loss due to cable attenuation is also less in the
structure of FIG. 2.
In unidirectional operation, the optical fiber 22 will have emitted
light 110 and affected light 110' moving in one direction on the
same fiber 22. In bidirectional operation, the optical fiber 22
will have emitted light 110 and affected light 110' moving in
opposite directions on the same fiber 22. Therefore, for
bidirectional operation, care must be taken in the selection of
components and in the installation techniques and quality to avoid
even minor reflections from any components or splices. These
reflections will appear as noise reflected back to the detector
circuit which depending on their amplitude could reduce the system
sensitivity or make certain types of measurements impractical.
Another network approach not shown but contemplated by the
invention includes a duplex concept that adds another fiber path
and set of switches to form a completely separate return path. For
example, a cable containing two separate fibers may be used to
create two individual parallel optical paths to form the duplex
optical network. A switching device for a duplex optical network
operation is shown in FIG. 10 and discussed in detail below. The
duplex approach with a dual fiber cable is also usable with the
star or hub type of structure shown in FIG. 2. This assumes that
both the source and the duplicate return hubs are located in the
same location. If this is not true then two separate fiber cable
systems must be run. Although this provides more flexibility in the
separation of the light source 100 and detector 200; it is also
potentially more expensive then installing twin fiber cable which
is a standard type of cable used in fiber based Ethernet type
communications systems (10BaseF or 100BaseFX). Duplex systems have
advantages of simplicity and more flexibility than the
unidirectional or bidirectional single fiber systems. Higher costs
due to the use of dual fiber cable and, more significantly,
duplicate sets of switches can, however, discourage this
approach.
A significant advantage of a unidirectional single fiber
architecture, like that used in a bus or ring network structure, is
that multiple locations can be sensed at the same time. This is
particularly useful for immediate detection of spills or the
presence of large gas or particle concentrations over a large
area.
In this approach, emitted light 110 is fed into the optical devices
60 of multiple rooms instead of selecting one room and bypassing
all the other rooms. This simultaneous monitoring concept is more
difficult to accomplish in bidirectional systems since the light
110 is reflected by the end sensor directly back to the detector.
In unidirectional systems, simultaneous sensing is made simple by
turning on multiple switches 50.
Gross detection of one or more external conditions from a group of
areas can be cascaded in a star or hybrid network by replacing one
or more of the electro-optical hub switches 500, 510, 520 by
optical star couplers such as JDS Fitel ACW series switches.
Couplers used in combination with optical switches such as shown in
FIG. 11 can provide simultaneous monitoring of many areas by again
simply turning on multiple optical switches simultaneously.
For example, subways, airports or other public places have a
plurality of areas where people can congregate. For example, in
airports, there are often a plurality of terminals where passengers
can board and exit aircraft. It is of considerable concern to
airport and other authorities that unscrupulous individuals could
seek to spread contaminants including biological or chemical agents
by exposing passengers or articles passing through open or confined
areas in the airport or other public places. By means of the
present invention, selective detection of contaminants can be
accomplished in preselected areas as described above or over a
broad range of areas.
If a bus structure is desired, but a star type wiring pattern is
preferred, a bus structure can be used that is wired in a star
structure. In this approach, each leg of the star structure is a
twin fiber cable where one fiber brings the light to the optical
switch 50 and the other fiber brings the light back to the star.
The star structure is used as a cabling junction to connect these
twin fibers together into a continuous series or bus structure.
This approach uses more cable than a direct point to point
approach, but it may provide more flexibility particularly if other
cables used for other purposes are being supplied to the same
locations.
Another approach to a star architecture replaces the switch hubs
500, 510, 520 shown in FIG. 2 with star couplers (1XN devices) 570
shown in FIG. 11. One example of this type of coupler (sometimes
known as a beam splitter) is a JDS Fitel ACW series Planer
Lightwave Circuit technology Waveguide Splitter. If in FIG. 2 the
Bldg Switch hub 500 and potentially also the Floor switch hubs 510
are replaced with 1XN couplers then the Sub floor hubs 520 act to
select the appropriate end node location to be sensed.
The added simplicity of this approach is counterbalanced by
increased loss from the coupler. Ideally the loss of a coupler is
directly related to the amount of outputs. For example, a 1X10
coupler would have a 10 dB attenuation. Typical values of actual
devices may in fact be slightly higher. If alternatively, all of
the hubs are replaced with star couplers then the end nodes must
also incorporate a simple SPST type switch 1100 as shown in FIG.
11.
FIG. 11 shows a star coupler 570 having five outputs 571, 572, 573,
574, and 575 used to replace the lowest level (either floor or
subfloor) hub switch in the system shown in FIG. 2. The star
coupler 570 has one input 576 connected to the fiber 22. FIG. 11
also shows an SPST switch element 1100 having a port 1130 connected
to port 573 of the star coupler 570 via fiber 22. The switch 1100
is switched on and light 110 exits the switch through port 1140 and
enters the optical device 60 where the light 110 is affected by an
ambient condition and exits the optical device as affected light
110'. The affected light 110' returns back through ports 1140 and
1130 and travels back through the coupler 570 and the rest of the
levels of star couplers (if more than one level is used) in the
photonic signal distribution network 20 to the optical detector
system 200. If this switch is not selected, the light 110 enters
the switch through port 1130 and is then absorbed in the switch or
shunted to a internal or external port 1120 where the light 110 is
absorbed by the switch or by some form of antireflection attenuator
or low reflectance optical terminator. An alternative approach to
implementing switch 1100 is one based on LCD or liquid crystal
display technology in which the light 110 is passed through an LCD
switch element that is either made transparent or opaque to
accomplish the transmission or absorption of light through the
switch.
In terms of performance regarding loss, a star coupler system with
125 nodes and three levels of 1X5 star couplers 570 would have a
theoretical loss from the hubs of 21 dB (3 times 7 dB per coupler)
plus an equivalent amount of return loss or another 21. When
another 1 dB is added for each pass through the SPST switch 1100
the total loss would be 44 dB. If hub switches are used as the end
devices instead of hub couplers and SPST switches, the loss can be
reduced to 30 dB.
The networked photonic signal distribution network 20 may also
include at least one optical amplifier 320 such as, but not limited
to, an erbium-doped optical-fiber amplifier anywhere along the
optical fiber 22 as shown in FIG. 1. The optical amplifier is used
to amplify the light within the optical fiber 22 to compensate for
loss that occurs in the light 110 and affected light 110' as the
photonic signal travels through the fiber and switches of the
photonic signal distribution network 20. The advantage of using
optical amplifiers is their ability to amplify a band of the
optical spectrum versus just one frequency by 20 to 40 dB.
Consequently many separate wavelengths of light can be faithfully
amplified and reproduced in frequency, phase and amplified
magnitude. Current units such as the erbium doped variety can
accommodate a wavelength range of 1.53 to 1.56 micrometers such as
the JDS Fitel Series EdFA-1300 units. Newer units from Lucent
Technologies can span 0.08 micrometers. The use of these amplifiers
is akin to a repeater in an electronic digital network. In the
photonic signal distribution system it allows a longer bus
structure or more optical switches to be used in the same network
thus allowing the common source and detector to be multiplexed over
many more measurement locations.
Amplifier units 320 are typically unidirectional devices, although
bidirectional units are possible. If unidirectional units are used
in a bidirectional system then two amplifiers must be used; one for
each direction. FIG. 14 shows a bidirectional amplifier 350 made
out of two unidirectional amplifiers 320. Optical isolators 330 are
used to maintain the proper direction through the respective
amplifier as well as to block the oppositely moving light. The 1X2
optical couplers 340 are used to split and couple the light back
together. Optical amplifiers either unidirectional or bidirectional
can be used in the central trunks of cascaded star or hybrid
systems. In a cascaded star coupler approach, a unidirectional or
bidirectional optical amplifier can be used advantageously at the
input of a large star coupler to compensate for their losses as
well as the losses of other system components.
Another approach to solving the attenuation problem in network
systems is the use of pulsed light. This solution involves emitting
a higher amount of power over a small portion of the entire pulse.
For example, one watt of signal power can be generated for only one
thousandth of the pulse period and still have a total average power
for the entire pulse width of 1 milliwatt making the emitted light
eye-safe.
Pulsed light is particularly applicable to a ring architecture
where the attenuation of the system is constant regardless of which
location is sensed. Consequently the pulse power can be easily set
to a constant value to always yield a good signal strength at the
detector. Architectures with a variable loss depending on the
location may need to have the source pulse power varied based on
the selected location, or the detector will need the ability to
handle large variances in the detected power without saturating or
overloading. Alternatively a variable attenuator, located for
example in front of the detector or the source, could be used that
has its attenuation or loss controlled based on the selected
location.
The location of the source of light 100 and detector 200 can be
varied. In a bidirectional implementation it is simplest to locate
the source 100 and detector 200 in the same location. An example of
a bidirectional common source, detection, and command unit is shown
in FIG. 9. An optical coupler 600 (or alternatively a circulator)
is used to connect both the source 100 and the detector 200 to one
fiber 22. If needed, optional optical isolator 330 can be used to
prevent the returning affected light 110' from reflecting off or
entering the source unit 100. Inside the source unit 100 is located
the actual light emitter 170 which may be either a broadband light
source, an LED, a laser, or some other light source operating at a
wavelength that can be transmitted through the optical fiber.
Through the use of materials such as plastic, silica, glass or
fluoride glasses, wavelengths covering the visible spectrum up into
the intermediate infrared light spectrum can be accommodated.
A source driver 180 is also shown which can control parameters such
as timing, amplitude, wavelength, phase and other characteristics
of the light emitter 170. Control can be accomplished by signals
and command information generated by the command unit 300.
Detection system 200 consists of a detector unit 270 having a
photodiode, or some other type of light detector, that is coupled
to a detector front end circuit 280 appropriate to the particular
optical detector 270. The front end 280 operates upon and converts
the detected signals from the detector unit 270 into a usable
signal or data format.
The detection system 200 may also utilize a processing unit 290
that contains circuitry or a computer unit to perform processing
and detection analysis to convert the output signals and
information from the detector front end 280 into user recognizable
data such as a PPM concentration level of a sensed gas or a
temperature in .degree. C. or humidity in % RH (Relative Humidity)
of the sensed space. Signals and command information needed to
operate the detector front end 280 and the processing unit 290 may
be provided by the command unit 300. Systems with a control network
24 and a command unit 300 will be connected to the control and data
communications units 310 through network 24 and used to control the
optical switches through the same connection. Higher level
functions such as a Graphical User Interface (GUI) with an operator
may be achieved through the command unit 300 which may be used to
execute commands from, or provide information to, such other
external interfaces and control systems as is required through a
connection 26 with other devices in the system 10 or other systems
in the building.
In another aspect of the invention, it may also be desirable to
locate the source 100 and detector 200 in different locations. For
example in a bus structure of the photonic signal distribution
system 20, it may be easier to locate the detector 200 at the end
of the bus rather than incur the extra optical fiber losses to run
a length of the fiber 22 from the last sensing point back to the
source location. Cabling and installation costs can be lowered by
this as well. Any coordination between the two devices can be done
by a dedicated electrical signal line or through the control and
communications network 24 that controls the optical switches 50,
500, 510, or 520.
Alternatively, a different configuration involves the light 110 of
a common source 100, or from one of potentially multiple dispersed
or remotely located centralized sources 100, switched to the
location 400 where air is to be sensed. However, rather than
sending the modified light 110' back into the fiber 22 and to a
common detector 200, there can be a light detection system composed
of a plurality of individual detection units 200 (or at least the
detector element 270 and potentially the detector 280 as well)
located near the sensed locations 400 to provide the detection
function locally. This approach provides an economical solution for
applications where the detector element 270 is an inexpensive
device (a photo-diode for instance) and the immediate signal
processing of element 280 can be done locally and economically at
the sensed location. For example, the airflow control electronics
already located in the room may be able to do the signal processing
with little added cost.
More complex processing of the signals, such as done by processing
unit 290, can still be done centrally in a computer or workstation
for example by sending the information back through the data
communications network 24. This approach may also be desirable
where the return optical path 22 is expensive in terms of
components and/or installation or would incur added insertion
losses. Required coordination between the source 100 and the
individual detectors 200 or units 270 and 280 may also be achieved
through the use of the control and communications network 24 which
is controlling the optical switches 50. This approach would be
useful in a cascaded star network using star couplers vs. switches
since having the detectors near the sensed locations 400
effectively cuts in half the significant power division losses of
this or other approaches by eliminating all the return losses.
In another aspect of the invention, similar to above, multiple
emitters 100 are located near the sensed locations 400 with the
light passing directly into the optical device 60. The multiple
emitter devices 170 may use a direct coupling from the emitter
device such as a Light Emitting Diode or Laser diode into the
sensed environment or air or it may pass through a short length of
fiber to get to the sensed air volume contained or sampled by the
optical device 60. Once the affected light 110' is passed though
the sensed volume it enters an optical fiber 22 and is routed
though the fiber network 20 using optical switches 50, 500, 510, or
520 to a centralized or common detector 200, or to one of
potentially multiple centralized detectors 200 that may be
dispersed or remotely located throughout the system. As with the
multiple localized detector system, this approach may be more cost
effective where the cost of extra fiber 22 and/or components and
resultant increased insertion loss would outweigh the cost of the
extra sources 100 (or equivalently optical detector elements 170
and their driver equipment 180). This approach may even be more
cost effective when the source is an inexpensive broadband LED or
inexpensive laser diode.
New Vertical Cavity Surface Emitting Laser diodes (VCSEL's), such
as made by Honeywell's Microswitch division for example are
relatively inexpensive and easy to drive yet have high output power
and narrow line width performance. For example, when sensing
particles a single LED or laser diode can be used that operates
continuously or is turned on when needed with virtually no special
control requirements. In this application, complex features can be
placed into the detection algorithms which are part of a
centralized computer and software system.
For multiple localized emitter applications the switching function
may be completely handled with on/off or pulsed control of the
emitter 170. Consequently fewer or potentially no optical switches
need be used in the network. In this specific case optical couplers
could be used to gather the signals throughout the network and sent
to common detector(s).
One of the advantages of the optical switch network concept is the
ability to dynamically reconfigure a network as described earlier
with the use of series bypass and hub/star type switches. Another
option available to even further extend the flexibility of this
type of approach is the availability of NXN or MXN type
cross-connect or matrix switches such as Dicon Fiberoptics GP700
series of fiber optic matrix switches. This can be particularly
useful if a system has multiple sources located throughout the
network and/or multiple detectors that are located in different
locations as well. Although not required, matrix switches are the
most general switch connection approach and they have the advantage
that they allow various separate networks to be combined
dynamically. For example, two separate sensing networks can be
combined from time to time to allow cross-checks of accuracy
between the systems by measuring the same location. Breaks in the
network can potentially be dynamically fixed by reconfiguring the
network around the break.
Optical Switches and Devices
The remotely distributed switches 50 can be configured in a variety
of forms to meet different network architectures and needs.
Similarly, optical devices 60 can include a number of different
forms for responding to different external conditions including
network approaches. The following are examples of remotely
distributed switches and optical devices that can be used with the
present invention.
Referring to FIG. 4, the hub switch 500 is a bidirectional
switching device having a common port 502 and at least two isolated
ports 504, and 506 for selectively switching the common
bidirectional port 502 to at least one of the isolated
bidirectional ports 504, or 506. The control of the switch is
through a control line 150 which commands the switch to one of it's
switched states The photonic signal distribution system 10 may
include a plurality of hub switches 500 which are typically
connected by means of an optical fiber 22 to other remotely
distributed switches 50 or 500 and optical devices 60. As explained
above, the electro-optical hub switches 500, 510, and 520 are
identical 1-X-n switching devices that are distinguished from one
another by their location and function in the network. An example
of a hub switch is a JDS Fitel series SK fiber optic switch
modules
FIG. 5 illustrates a DPDT type optical switch 50 configured to be
used in a unidirectional bus or ring structured network to connect
an optical fiber 22 to an optical device 60 and an optical bypass
47. The optical switch 50 has a plurality of optical ports 41, 42,
43, 44, 48, 49. The state of the would be commanded through control
connection 150 which is provided a control signal that would
typically be of an electrical nature. The optical switch 50 is
connected to the optical distribution network 20 by means of the
optical fiber 22 which is coupled to one set of the optical ports
41, 44.
In one aspect of the invention, an optical switch 50 as shown in
FIGS. 4, 5, 6, 8, 10, 11, and 12 can be controlled by control
signals which would typically be electrical in nature. These
signals are provided to the optical switch 50 by an electrical
connection 150 from a control and data communications device 310
that is connected to an existing electrical network (not shown), or
a new electrical network 24 such as that shown in FIG. 1. The
control and data communications device 310 in turn receives its
commands from data generated by a command unit 300. Alternate
physical control signal formats could be of an analog or digital
signal format in electrical, pneumatic, radio frequency (wireless),
or optical form.
In response to the control signal on line 150, the optical switch
50 shown in FIG. 5 switches the light 110 on the optical fiber 22
to an optical device 60 coupled to another set of optical ports 42,
43 or to an internal or external optical fiber by-pass 47 coupled
to yet another set of optical ports 48,49. The optical device 60 is
designed to change the light in response to a detected condition or
substance. The affected light 110' contains information related to
the area proximate to the optical device 60 and is directed to the
detection system 200 by means of the optical fiber 22 and the
electro-optical switch 50.
FIG. 6 illustrates an optical switch 550 used in a bidirectional
bus or ring architecture to connect a bidirectional optical fiber
22 to a bidirectional optical circulator 600 having a two port
optical device 60 such as a transmissive gas sensing cell. The
optical switch 550 is the optical equivalent to a traditional
single pole two position (SPDT) electrical switch. The optical
switch 550 has a plurality of optical ports 552, 554, 556 and a
control connection 150. The optical switch 550 is connected to the
optical distribution network 20 by means of the optical fiber 22
which is coupled to one optical port 552. The optical switch 550
couples or bypasses the bidirectional optical circulator 600 and
two port optical device 60 with respect to the optical fiber
22.
An example of a SPDT optical switch is a JDS Fitel series SW
optical switch. Optical switch configurations can also be built
using other technologies such as planar or silica based waveguide
technology or the fruitful area of micro-machined devices such as
micro-machined mirror switch technology such as those developed by
Texas Instruments. Another variation of optical switches is
manufactured by AMP corporation which uses center-symmetrical
reflective (CSR) optics. Other technologies such as single mode
thermo-optic switches utilizing a Mach-Zehnder interferometer
manufactured by Photonic Integration Research are also commercially
available. Future approaches such as those that might involve a
light beam to switch another light beam may also be possible.
Simple SPST type switches, such as shown in FIG. 11 can also be
implemented with LCD technology.
In response to a control signal the optical switch 550 switches the
light 110 on the optical fiber 22 to the optical circulator device
600. The optical circulator device 600 can be any commercially
available device such as a JDS Fitel CR2300 series optical
circulator. The function of the optical circulator 600 is to send
the light 110 from the photonic distribution network 20 through the
optical device 60. The circulator then changes the direction of the
light sending it back down the optical port 556 of the optical
switch 550. This creates a bidirectional modified photonic signal
110' that will travel back down the same path it came to the source
100 and detector 200 unit. When the optical circulator 600 and
optical device 60 are bypassed, the optical fiber 22 is coupled to
optical switch 550 through ports 552, 554.
The optical device 60 associated with the optical circulator 600 is
designed to change the light in response to a detected condition or
substance. The affected light 110' contains information related to
the area proximate to the optical device 60 and is directed to the
detection system by the optical fiber 22 by means of the optical
circulator 600 and electro-optical switch 550.
FIG. 7 illustrates a one port optical device 700 having a
reflective gas sensing cell 750 that represents one form of an
optical device 60. The one port optical device 700 includes a
multiply reflective transmissive sensing cell 750 for
multiply-reflecting and changing the light 110 according to the
environment entering the sensing cell 750 through its inlet 710 and
outlet 720. A terminal reflective device 740 is provided for
reflecting the affected light 110' out of the cell 750 by means of
the port 730 coupled to the optical fiber 22.
FIGS. 15A-15C illustrate different ways that the an optical device
60 in general (and specifically for example with the gas sensing
cell 750 of FIG. 7) can be used to measure gases or other
environmental measures such as particulates, humidity, temperature,
or others.
FIG. 15A illustrates a configuration for taking an averaged sample
from an exhaust duct flow. The input and output ports 710 and 720
of gas sensing cell 750 are connected through a pair of pressure
taps 1303 and 1305 respectively to straddle an exhaust valve 1300
in the exhaust duct in which the sample is taken. Instead of
straddling an exhaust valve 1300, the gas sensing cell 750 could
also be connected to straddle another device which creates a
pressure drop within an air flow. For example, the gas sensing cell
750 could straddle an airflow controller, a damper, an orifice
ring, an elbow or simply a restricted length of duct. Assuming the
air flow through the exhaust valve 1300 to be in a direction F,
there is a high relative air pressure at pressure tap 1303 and a
low relative air pressure at pressure tap 1305. Therefore, a small
portion of the air flow through exhaust valve 1300 is bled off by
pressure tap 1303, and diverted into the gas sensing cell 750. Some
of the air already in the gas sensing cell 750 is returned to the
exhaust flow, just downstream of the exhaust valve 1300. The sample
in the gas sensing cell 750 contains a mixture of air from the
flow, retained in the gas sensing cell 750 for a period of time.
The sample thus forms an average of the contents of the flow over
the period of time.
As shown in FIG. 15B, the gas sensing cell 750 may be connected to
a sampling head 1311 located within the space whose air quality is
of concern, instead of pressure tap 1303. This configuration will
measure the average flow of airborne substances from the space that
is exhausted by exhaust valve 1300, e.g. a room.
In yet another variation, there is shown in FIG. 15C a gas sensing
cell 750 connected to straddle an air supply valve 1350 or another
element causing a pressure drop in the duct air flow. This system
operates similarly to that discussed above in connection with FIG.
15A, but measures and averages the air flow in a supply duct,
rather than in an exhaust duct. This may be useful for discovering
cross-contamination from other parts of an air management system,
defects in the air supply system, or for controlling the make-up
air supply in response to an emergency condition detected
elsewhere.
An alternative approach to the use of a separate gas sensing cell
is to integrate the optical path of the light beam into an air
valve itself of the type shown in FIG. 15 or of a damper or of
another air flow control device or even of a section of duct work.
FIG. 16 illustrates an example of how this is done with the fiber
22 coming most likely from some optical switch 50, 550 or 500, etc.
Elements 1322 and 1323 are mirrored surfaces to create a multiple
path such as is shown in the gas sensing cell of FIG. 7. After
crisscrossing the duct one or more times the light from the fiber
is reflected back into the fiber 22. Alternatively the light may
only cross the duct once or multiple times but is picked up at the
opposite side of the duct (not shown) and sent down the fiber 22 in
a unidirectional system. To help with emitting and the collecting
of the light, lens 1321 may be used to widen the emitted beam and
narrow the collected beam to create a wider beam to cross the duct.
One advantage of the approach shown in FIG. 16 is that it can be
used to sense the average air velocity in the duct and thus also
the air volume in the duct using laser velocimetry which uses the
sensed Doppler shift of particles in the air to sense the velocity
of the air itself.
FIG. 8 illustrates an optical switch such as the optical switch 550
shown in FIG. 6 connecting a bidirectional optical fiber 22 to a
one port optical device such as the reflective gas sensing cell 700
shown in FIG. 7.
One approach to implementing a bidirectional version of the common
source detection and command system 30 in FIG. 1 is shown in FIG. 9
which illustrates a bidirectional optical circulator 600 (or
alternatively a 1X2 optical coupler could also be used instead)
connected to a source of light 100, a detector system 200, and a
command unit 300.
The optical fiber 22 of the optical distribution network 20 is
coupled to the optical circulator 600 at port 1616. The detector
system 200 and the source of light 100 are coupled to the optical
circulator 600 at port 2612 and port 3614 respectively. The source
of light 100 and detector system 200 are coupled to a command unit
300 which controls their operation.
The light source 100 generates light 110 which is coupled to the
optical fiber 22 of the optical distribution network 20 by the
optical circulator 600. The light 100 is effected by an external
condition proximate to some optical device coupled to the optical
distribution network 20. The affected light 110' is coupled onto
the optical fiber 22 and directed back to port 1616 of the optical
circulator 600. The optical circulator 600 directs the affected
light 110' to the detector system 200 which detects the condition
and provides outputs to the command unit 300. An alternate
embodiment of FIG. 9 replaces the optical circulator 600 with a
potentially cheaper 1X2 optical coupler to achieve the same result
but with the disadvantage of some additional loss caused by the
coupler.
The source of light 100 of FIG. 9 could include an LED or Laser
diode or some other form of illumination 170 coupled to a driver
circuit 180. The detector system 200 could include a photodiode
detector or some other device 270 to measure the intensity of light
coupled to a set of detector electronics 280 to refine the
photodiode or other suitable detector's output in order to generate
a meaningful output signal related to the received light intensity.
This signal can then be processed by a CPU or special signal
processor 290 to output a calibrated output signal 291 that is
directly readable in some appropriate engineering units. Both the
source system 100 and the detector system 200 are controlled and
coordinated by the command unit 300. This command unit 300 also
analyzes the operating parameters of the light source, the photonic
signal distribution network, the pertinent optical devices and the
received signals of the detector in order to generate a meaningful
qualitative and/or quantitative measure of the level of
environmental gas concentrations, biological agents, particles,
temperature, humidity, pressure, displacement, air velocity, and
proximity or location of objects including people which can affect
the sensed parameter at the sensed location. This information can
then be communicated to the operator by a graphical user interface
or through a data communications interface connection 26 to another
system such as a building control and management system (BMS)
having its own Graphical User Interface or other means of
communicating with a user or operator.
FIG. 10 illustrates a six port duplex optical switch 1000
connecting an optical device 60 and two optical fibers 22a, 22b
operating in a duplex optical network (not shown). A duplex optical
network is similar to the optical distribution network 20 shown in
FIG. 1. except that it has two optical fibers. The duplex optical
switch 1000 allows full duplex operation of the duplex optical
distribution network, providing a feed optical fiber 22a and a
return optical fiber 22b. Light 110 is provided by the feed optical
fiber 22a to the input port 1010 of the duplex switch 1000. The
light 110 can be switched by the duplex switch 1000 to the duplex
optical distribution network and another duplex switch 1000, or to
an optical device 60 as shown in FIG. 10. The light 110 is effected
by optical device 60 and the affected light 110' is directed to the
return optical fiber 22b to a previous duplex switch (not shown)
where it continues to a detection system.
Another type of optical device 60 involves the use of optical fiber
sensor structures. In these sensor approaches the light stays
substantially in the fiber and is modified in some way by the
specially designed fiber's interaction with it's surrounding
environment. For example a porous type of cladding material can be
used such that as the fiber cladding absorbs different materials
such as water vapor or chemical vapors, the loss of the fiber is
changed due to the change in the fiber cladding's index of
refraction. Alternatively if the fiber is stretched or bent by
environmental forces such as air velocity or pressure or
displacement the fiber's loss can also be changed.
Alternatively, many various types of optical sensor devices and
methods have and continue to be developed that modify light in some
way based on environmental conditions. Examples of some of these
devices include Michelson-type interferometric sensors, vibrating
beam micro-machined sensors developed for example by Honeywell,
fiber Bragg grating sensors, Fabry-Perot interferometric sensors,
or the related in-line fiber Etalon (ILFE) sensors. Any of these
devices could be put in the space to be sensed and then the
processing circuitry can be multiplexed as described
heretofore.
In another implementation of the invention, an optical device 60
can also include a another alternative form of smart optical fiber
structure that involves coating the end of a fiber to be exposed to
the environment with various special chemical or biological
materials that are affected in some way by the environment.
Specifically these sensors have specially designed surfaces or
fiber ends that can detect pre-selected conditions such as gases,
biological agents, and other airborne matter. One manner by which
this can be implemented involves using a special light source 100
located in the remote unit 30 of for example FIG. 1 that sends this
light down the fiber 22 and through the optical switches 50 to the
optical sensor device 60 as described above. This light in the
presence of the material to be sensed reacts together with the
coated chemical in some way such as fluorescing. The changed or
fluorescent light is then carried back down the same fiber or a
duplex fiber path to an optical detector 200 which detects the
amount of changed or perhaps fluorescent light. These devices are
described in detail in Jane A. Ferguson and David R. Walt, Optical
Fibers Make Sense of Chemicals, Photonics Spectra, March 1997; Eric
Udd, Applications of Fiber Optic Smart Structures, ISBN#
0-7803-3277-6; and R. A. Lieberman, Distributed and Multiplexed
Chemical Fiber Optical Sensors, SPIE Vol. 1586 (1991) which are
incorporated herein by reference.
The preceding sensor strategies or other approaches may be combined
to measure multiple parameters such as air velocity, temperature,
pressure, multiple gases etc. at a given sensed location. Other
parameters that could also be sensed include viable organisms such
as microbial or bacteria infestations or fungus growth which may be
detected for example, through the sensing of certain VOC's given
off by these organisms.
If fiber sensors are used for example, multiple fiber segments may
be used in series or in parallel in conjunction with two couplers
(one acting as a beam splitter and the other to couple the
different segments back to a common fiber). Alternatively,
wavelength division or time division multiplexing can also be used
at the site to multiplex multiple sensors in order to sense
multiple parameters simultaneously. Alternatively, a 1XN Hub
optical switch could also be used at the desired location to select
one of a set of sensors.
From an application standpoint, many functions and sensed
parameters can be performed simultaneously. For example, an optical
device 60 could consist of a device to send a beam crisscrossing
across a doorway before it is captured and sent back down the fiber
network 20. This simple sensor approach could be simultaneously
used to sense the concentrations of various gases in the air
passing through the doorway, the velocity of air passing through
the doorway, the presence of smoke in the environment through the
obscuration of the light or else by sensing for the gaseous
components of combustion, size and amount of airborne particles,
and even security considerations by sensing for momentarily
obstructions of the beam caused by someone passing through the
doorway.
Similarly, a light beam could be sent in a one pass or multiple,
crisscross path across the opening of a laboratory fume hood in
order to simultaneously sense multiple parameters. For example, the
amount of containment or similarly the amount of loss of
containment could be measured by analyzing the gases that pass
through the beams crossing the hood opening. Fume hood face
velocity could also be measured as well the amount of particles in
the air. Depending on how much coverage exist of the beams across
the opening, the presence of a person reaching into the hood could
also be detected. A direct measure of containment could also be
measured by releasing a known amount of measurable, tracer gas in
the hood with the light beams used to detect how much of the gas
passes through the hood opening into the environment. Although less
sensitive this measurement of the tracer gas could also be done in
a general exhaust air stream as discussed above in FIG. 16 to look
for larger loss of hood capture. Similar to above, a hood or lab
fire could be detected by measurement of the smoke gases and
particles passing through the light beams of a hood opening or of a
general exhaust valve
Data Communication and Control
Appropriate communication and signal processing techniques are
employed in the invention to ensure coordination of the source and
the detected light signals as well as that the proper switches are
actuated and that the desired affected light signals from the
sensed locations are properly detected and identified.
The command unit 300 coordinates the operation of the remotely
distributed switches 50 (or other optical switches 500, 510, 520,
550, etc.) associated with the photonic signal distribution system
10. The command unit 300 generates preselected data signals that
command the remotely distributed switches 50 to operate as
required. The remotely distributed switches 50 can be controlled
directly or by means of a plurality of data communication and
control devices 310. By directly, it is meant control cables that
are directly connected in a point to point connection between
command unit 300 and the respective optical switch 50. A separate
cable would be used per optical switch thereby creating a mass of
cables emanating from the command unit 300 to all the respective
optical switches 50.
Another control approach for the optical switches 50, would involve
either minimal or no control via the command unit 300 or just some
form of simple synchronizing of the optical switches in which they
are self controlled or operated through a preset sequence. For
example, upon power up the optical switches could operate in some
form of preprogrammed sequence where each switch in turn switches
on to route its affected light 110' back to the detector 200. A
unique code such as a varying switch on time could be assigned to
each switch so that the command unit 300 could determine where the
light signal 110' came from without need to control or even
synchronize the optical switches' operation.
A potentially more powerful and more flexible approach uses the
data communication and control devices 310 that are connected
together in some form of electrical wire, wireless (RF), power line
carrier, or optical fiber data communications network with each
other and command unit 300. The data communication and control
devices 310 are in turn directly connected (or potentially
connected through some form of other data communications network)
with the remotely distributed switches 50 for controlling their
operation in response to the preselected data signals that
originate from the command unit 300 or potentially from another
data communication and control device 310. The communication and
control devices 310 can be proximate to or incorporated into the
remotely distributed switches 50. In addition, the number of
communication and control devices 310 can be equal to or not the
same as the number of remotely distributed switches 50. For
example, the data communication and control devices 310 may control
more than one of the optical switches 50.
The data communication and control devices 310 may include
non-dedicated modules or software which perform functions in
addition to operating the optical switches 50. For example, the
non-dedicated modules or software can perform functions such as
controlling devices unrelated to the networked photonic signal
distribution system 10 such as, but not limited to, laboratory fume
hood controls, room pressurization controls, room temperature
controls, or be part of the building control and management
systems. Alternatively, the data communication and control devices
310 may be part of a local area network of distributed Personal
Computers (PCs) or computer workstation that are connected together
in a data communications network. The data and communication
control devices 310 could be separate devices in this local area
network or be incorporated into the functions of the PCs or
computer workstation themselves.
In another implementation of the present invention, the preselected
data signals are generated by the command unit 300 and communicated
to the data communication and control devices 310 over the same
optical fiber 22 of the optical distribution network 20. The
preselected data signals are generated in electrical or optical
format by the command unit 300 and provided to the light source 100
which encodes the preselected data signals within the light 110
that is sent out onto the optical fiber 22. The preselected data
signals in optical form can be at a wavelength different from the
wavelengths of the light distributed by the optical distribution
network. The light distributed by the optical distribution network
itself can also be used to create the preselected data signals in
optical form.
For example the light emitted by the source 100 for purposes of
environmental monitoring could be preceded by a rapid set of short
pulses or a digital word comprised of short and long pulses or
through the length of the pulse could be used to address and divert
the beam to a desired location by having a specific "address" for
each location. The amount of time to sense at the location could be
preprogrammed or could also be commanded though a second digital
word transmitted after the address. For example two pulses could be
transmitted the first is of a length that indicates the particular
address, the other indicates the length of the sensing period.
After the signaling is completed the optical source beam would then
be used to sense the air at the indicated location. Multiple
locations in a unidirectional series or ring based implementation
could be simultaneously sampled with this approach as well by
having certain address groupings that would turn on more than one
switch.
The above approach could be implemented through an approach shown
in FIG. 12 which illustrates an optically controlled switch system
1200 that operates the optical switches without need for a separate
data communications network 24 or data communications units 310.
This system contains a coupler 1210, a switch controller 1250, and
an optical switch 1220 providing a through path to another switch
(not shown) and an optical device 60. The coupler 1210 may be a
high ratio coupler tap such as the JDS FITEL AC0199 Coupler which
is a 1/99 ratio monitor coupler specifically designed for tap or
monitoring applications. The switch controller 1250 is coupled to
the light 110 having a control signal 110b embedded in the light
110. The switch controller 1250 is controlled by the light control
signal 110b which is typically generated by the command unit 300. A
photo-detector of some type 1270 detects the light signal 110b and
sends the corresponding electrical information to the switch
controller element itself 1280. The switch controller 1250 controls
the optical switch 1220 through it's control line input 150. When
activated by this control line 150 the optical switch 1220 couples
the light 110 to the optical device 60 where it is effected by the
ambient condition. The affected light 110' is than coupled back
through the optical switch 1220 and onto the optical distribution
network 20 by means of the optical fiber 22.
In another example the light beam 110 itself could trigger the
operation of successive switches operating in a bus configuration
such as shown in FIG. 1 and FIG. 12. As each optical switch 1220
such as those shown in is in turn hit by entering light 110, it
detects or is energized by that light 110 through switch controller
1250 to operate by switching on to route the light 110 to the
optical device 60 and then to send the affected light 110' back to
the optical detector 200. Switch controller 1250 then further acts
after a preset period of time to switch the optical switch 1220 to
bypass the light 110 to the next optical switch 1220 in the series
configuration of the bus network structure to repeat the same
sequence of operation with the next optical switch 1220 and optical
device 60. In another aspect of the present invention, a plurality
of independent networked photonic signal distribution system 10 can
be linked together. This feature provides greater network
flexibility and allows such things as larger network schemes,
specialized networks for monitoring particular conditions, and
improved system performance and accuracy by reducing or shifting
the load on any one command unit 300, light source 100, or
detection unit 200. In addition, the command units 300 and data and
communication control devices 310 described above can include a
programmable device such as a computer.
Wavelength-division Multiplexing (WDM)
In another aspect of the invention, the networked photonic signal
distribution system 10 may include communication and signal
processing techniques such as, but not limited to,
wavelength-division multiplexing (WDM). This technique provides
expanded use of system bandwidth by allowing for signal
discrimination as a function of wavelength. WDM is more fully
described in Alan Eli Willner, Mining the Optical Bandwidth for a
Terabit per second, IEEE Spectrum, April 1997 and Alan D. Kersey,
Multiplexed Fiber Optic Sensors, SPIE Vol. 1797 (1992) which are
incorporated herein by reference.
Very briefly in summary, this approach involves transmitting data
on many different wavelengths. Multiple signals with even small
wavelength differences on the order of even 5 to 10 nanometers can
be used to separate data streams. These streams can then be routed
to different locations by star type routers or hubs where a variety
of techniques can be used to effectively demultiplex the signal and
split out the different signals if desired onto different outputs
of the router based on the wavelength of the signal. This
demultiplexing can be done by many techniques such as interference
filters, or GRIN-rod lenses. An example of a commercial product
that involves cascaded interference filters is the WD5555 E/W
product series manufactured by JDS Fitel.
For example, the networked photonic signal distribution system 10
can have a source of light 100 that generates light 110 having a
plurality of wavelengths as shown in FIG. 13. This figure
illustrates a plurality of common source detection and command
system 30 in a wavelength division multiplex configuration 1300.
The wavelength division multiplex configuration 1300 includes a
bidirectional dense wavelength division multiplexer 1310 such as,
but not limited to, a JDS Fitel WD5555B. A plurality of wavelengths
are preselected, such as 850 nm, 960 mn, 1200 nm and 1550 nm, that
are used throughout a photonic signal distribution system 20. The
ports 1320, 1330, 1340, 1350 of the wavelength division multiplexer
1310 are coupled to a plurality of bidirectional circulators or
couplers 1311a,b,c,d respectively. The plurality of circulators or
couplers 1311a,b,c,d couples light 110a,b,c,d produced by a
plurality of light sources 100a,b,c,d to the photonic signal
distribution system 20 where it is effected by a plurality of
optical devices (not shown). The affected light 110'a,b,c,d is
returned to the wavelength division multiplexer 1310 and separated
by wavelength and coupled by ports 1320, 1330, 1340, 1350 to the
plurality of circulators or couplers 1311a,b,c,d. The affected
light 110'a,b,c,d is provided to a plurality of detector systems
200a,b,c,d where it is detected and analyzed by a plurality of
command units 300a,b,c,d. The operation of the command units
300a,b,c,d may be further controlled by a CPU 1380.
It will be appreciated that the present invention provides a highly
flexible, highly adaptable signal distribution system which enables
rapid detection of and response to environmental conditions. In
addition, the invention's networked nature greatly reduces
complexity and cost of environmental detection and control systems.
These and other advantages of the present invention will be
apparent to those skilled in the art from the foregoing
specification.
The present invention may be embodied in other specific forms
without departing from the spirit or essential attributes thereof
and, accordingly, reference should be made to the appended claims,
rather than to the foregoing specification, as indicating the scope
of the invention.
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